When the bad guys are good, and the good guys are bad

In the short story An Occurrence at Owl Creek Bridge, the reader is forced to ask if there really is a clearly drawn line between good and bad, and whether something "evil" can actually be good.

Instead of the obvious, I, going to write about how sometimes what is known to be evil, can be good, and how the truth gets a little grey. 

 The story starts off with a man about to be hung, and you immediately feel bad for him, especially since he apparently good guy, described as  having "a kindly expression... Evidently this was no vulgar assassin."(3) Also, the planter thinks about his family before he is about to die, which made me think of my father. Yet this man is later revealed to be a slave owner, who wants to keep slavery/succeed. All these facts make him evil, deserving the death. right? Except you can't help but think about how all he wants is to be with his family. Even though he is a slave owner, as I read I couldn't help but hope he made it out alive.  I actually found myself rooting against the soldiers, who were  the good guys. So even though the real twist was that the  escape was fake,  I ask a question about truth and lies in this piece of literature. Even when something is accepted as evil, can this known truth become blurred when the person is good?